Add HTTP::Server::Context#socket

This allows to determine the client connection when a `HTTP::Server` binds
to multiple interfaces.

spec/std/http/server/server_spec.cr

@@ -240,7 +240,11 @@ module HTTP
 
     it "binds to different ports" do
       server = Server.new do |context|
-        context.response.print "Test Server (#{context.request.headers["Host"]?})"
+        socket = context.socket
+        socket.should be_a(TCPSocket)
+        if socket.is_a? TCPSocket
+          context.response.print "Test Server (127.0.0.1:#{socket.local_address.port})"
+        end
       end
 
       tcp_server = TCPServer.new(0)
@@ -266,6 +270,7 @@ module HTTP
       processor = HTTP::Server::RequestProcessor.new do |context|
         context.response.content_type = "text/plain"
         context.response.print "Hello world"
+        context.socket.should be_nil
       end
 
       input = IO::Memory.new("GET / HTTP/1.1\r\n\r\n")

src/http/server/context.cr

@@ -7,8 +7,11 @@ class HTTP::Server
     # The `HTTP::Server::Response` to configure and write to.
     getter response : Response
 
+    # An optional `Socket` which holds the client connection of this context.
+    getter socket : Socket?
+
     # :nodoc:
-    def initialize(@request : Request, @response : Response)
+    def initialize(@request : Request, @response : Response, @socket : Socket? = nil)
     end
   end
 end

src/http/server/request_processor.cr

@@ -33,7 +33,12 @@ class HTTP::Server::RequestProcessor
         response.version = request.version
         response.reset
         response.headers["Connection"] = "keep-alive" if request.keep_alive?
-        context = Context.new(request, response)
+
+        if input.is_a?(Socket)
+          context = Context.new(request, response, input)
+        else
+          context = Context.new(request, response)
+        end
 
         begin
           @handler.call(context)